inspired-by-fsharp/tests/Unit/ResultTest.php

<?php
/**
 * @author Daniel J. Summers <daniel@bitbadger.solutions>
 * @license MIT
 */

declare(strict_types=1);

use BitBadger\InspiredByFSharp\{Option, Result};

describe('->ok', function () {
    test('returns OK value for OK result', function () {
        expect(Result::OK('yay')->ok)->toBe('yay');
    });
    test('throws an exception for Error result', function () {
        expect(fn() => Result::Error('whoops')->ok)->toThrow(InvalidArgumentException::class);
    });
});

describe('->error', function () {
    test('throws an exception for OK result', function () {
        expect(fn() => Result::OK('yeah')->error)->toThrow(InvalidArgumentException::class);
    });
    test('returns Error value for Error result', function () {
        expect(Result::Error('boo')->error)->toBe('boo');
    });
});

describe('->isOK', function () {
    test('returns true for OK result', function () {
        expect(Result::OK('ok')->isOK)->toBeTrue();
    });
    test('returns false for Error result', function () {
        expect(Result::Error('error')->isOK)->toBeFalse();
    });
});

describe('->isError', function () {
    test('returns false for OK result', function () {
        expect(Result::OK('fine')->isError)->toBeFalse();
    });
    test('returns true for Error result', function () {
        expect(Result::Error('not ok')->isError)->toBeTrue();
    });
});

describe('->bind()', function () {
    test('returns OK when binding against OK with OK', function () {
        expect(Result::OK('one')->bind(fn($it) => Result::OK("$it two")))
            ->isOK->toBeTrue()->ok->toBe('one two');
    });
    test('returns Error when binding against OK with Error', function () {
        expect(Result::OK('three')->bind(fn($it) => Result::Error('back to two')))
            ->isError->toBeTrue()->error->toBe('back to two');
    });
    test('returns Error when binding against Error', function () {
        $original = Result::Error('oops');
        $result   = $original->bind(fn($it) => Result::OK('never mind - it worked!'));
        expect($result->isError)->toBeTrue()
            ->and($result)->toBe($original);
    });
});

describe('->contains()', function () {
    test('returns true when OK is strictly equal', function () {
        expect(Result::OK(18)->contains(18))->toBeTrue();
    });
    test('returns false when OK is not strictly equal', function () {
        expect(Result::OK(18)->contains('18'))->toBeFalse();
    });
    test('returns true when OK is loosely equal', function () {
        expect(Result::OK(18)->contains('18', strict: false))->toBeTrue();
    });
    test('returns false when OK is not loosely equal', function () {
        expect(Result::OK(18)->contains(17, strict: false))->toBeFalse();
    });
    test('returns false for Error', function () {
        expect(Result::Error('ouch')->contains('ouch'))->toBeFalse();
    });
});

describe('->exists()', function () {
    test('returns true for OK when condition matches', function () {
        expect(Result::OK(14)->exists(fn($it) => $it < 100))->toBeTrue();
    });
    test('returns false for OK when condition does not match', function () {
        expect(Result::OK(14)->exists(fn($it) => $it > 100))->toBeFalse();
    });
    test('returns false for Error', function () {
        expect(Result::Error(true)->exists(fn($it) => true))->toBeFalse();
    });
});

describe('->map()', function () {
    test('maps value for OK', function () {
        expect(Result::OK('yard')->map(fn($it) => strrev($it)))
            ->isOK->toBeTrue()->ok->toBe('dray');
    });
    test('throws an exception for OK when mapping result is null', function () {
        expect(fn() => Result::OK('not null')->map(fn($it) => null))->toThrow(InvalidArgumentException::class);
    });
    test('does nothing for Error', function () {
        $tattle = new class { public bool $called = false; };
        $error  = Result::Error('nope');
        $mapped = $error->map(function () use ($tattle)
        {
            $tattle->called = true;
            return 'hello';
        });
        expect($mapped)
            ->isError->toBeTrue()
            ->and($tattle->called)->toBeFalse()
            ->and($mapped)->toBe($error);
    });
});

describe('->mapError()', function () {
    test('does nothing for OK', function () {
        $tattle = new class { public bool $called = false; };
        $ok     = Result::OK('sure');
        $mapped = $ok->mapError(function () use ($tattle)
        {
            $tattle->called = true;
            return 'hello';
        });
        expect($mapped)
            ->isOK->toBeTrue()
            ->and($tattle->called)->toBeFalse()
            ->and($mapped)->toBe($ok);
    });
    test('maps value for Error', function () {
        expect(Result::Error('taco')->mapError(fn($it) => str_repeat('*', strlen($it))))
            ->isError->toBeTrue()->error->toBe('****');
    });
    test('throws an exception for Error when mapping result is null', function () {
        expect(fn() => Result::Error('pizza')->mapError(fn($it) => null))->toThrow(InvalidArgumentException::class);
    });
});

describe('->iter()', function () {
    test('iterates for OK', function () {
        $target = new class { public mixed $called = null; };
        Result::OK(77)->iter(function ($it) use ($target) { $target->called = $it; });
        expect($target->called)->toBe(77);
    });
    test('does nothing for Error', function () {
        $target = new class { public mixed $called = null; };
        Result::Error('')->iter(function () use ($target) { $target->called = 'uh oh'; });
        expect($target->called)->toBeNull();
    });
});

describe('->toArray()', function () {
    test('returns a one-item array for OK', function () {
        expect(Result::OK('yay')->toArray())->not->toBeNull()->toBe(['yay']);
    });
    test('returns an empty array for Error', function () {
        expect(Result::Error('oh no')->toArray())->not->toBeNull()->toBeEmpty();
    });
});

describe('->toOption()', function () {
    test('returns a Some option for OK', function () {
        expect(Result::OK(99)->toOption())->isSome->toBeTrue()->value->toBe(99);
    });
    test('returns a None option for Error', function () {
        expect(Result::Error('file not found')->toOption())->isNone->toBeTrue();
    });
});

describe('->tap()', function () {
    test('is called for OK', function () {
        $value = '';
        $original = Result::OK('working');
        $tapped = $original->tap(function (Result $it) use (&$value) {
            $value = $it->isOK ? 'OK: ' . $it->ok : 'Error: ' . $it->error;
        });
        expect($value)->toBe('OK: working')->and($tapped)->toBe($original);
    });
    test('is called for Error', function () {
        $value    = '';
        $original = Result::Error('failed');
        $tapped   = $original->tap(function (Result $it) use (&$value) {
            $value = $it->isOK ? 'OK: ' . $it->ok : 'Error: ' . $it->error;
        });
        expect($value)->toBe('Error: failed')->and($tapped)->toBe($original);
    });
});

describe('::OK()', function () {
    test('creates an OK result for a non-null value', function () {
        expect(Result::OK('something'))->isOK->toBeTrue()->ok->toBe('something');
    });
    test('throws an exception for OK with a null value', function () {
        expect(fn() => Result::OK(null))->toThrow(InvalidArgumentException::class);
    });
});

describe('::Error()', function () {
    test('creates an Error result for a non-null value', function () {
        expect(Result::Error('sad trombone'))->isError->toBeTrue()->error->toBe('sad trombone');
    });
    test('throws an exception for Error with a null value', function () {
        expect(fn() => Result::Error(null))->toThrow(InvalidArgumentException::class);
    });
});